Astronomical Tables and Formulæ Together with a Variety of Problems Explanatory of Their Use and Application: To which are Prefixed the Elements of the Solar System |
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Common terms and phrases
A.cos a.sin annual apparent diameter apsides ascending node assumed equal astronomer barometer centre commencement computing considered as unity correction deduced degree denotes determined Diff difference earth being considered eccentricity ecliptic ephemeris Equal Altitudes equinoxes Fahr formula given angle given side greatest equation Greenwich h m h m half the major horizontal parallax hour angle Interval Log Jupiter Laplace latitude logarithms lunar major axis mean anomaly mean distance mean longitude mean motion mean sidereal revolution mean solar days mean synodical revolution Mercury meridian minus when South moon moon's node motion in 365 Nautical Almanac nearly nutation Obliq observations orbit is inclined p.sin pendulum perihelion phænomenon planet Pole precession present century quantity refraction retrograde Right Ascension satellites Saturn secular variation semidiameter sexagesimal sin² sin³ solar nutation solstice sun considered sun's syzigies Table thermometer tion true longitude Uranus Venus whence zenith distance
Popular passages
Page 20 - The astronomical, or civil, day is constantly changing. This variation arises from two causes; 1. The unequal motion of the earth in its orbit ; 2. The obliquity of that orbit to the plane of the equator. [The mean and apparent solar days are never equal, except when the sun's daily motion in right ascension is 5g
Page 6 - These laws are, 1°. The orbit of each planet is an ellipse; of which the sun occupies one of the foci. 2°. The...
Page 7 - In this case, it is obvious that the plane of the circle of illumination would be perpendicular to a line drawn from the centre of the sun to the centre of the earth...
Page 57 - From the singular analogy, above alluded to, it follows that (for a great number of years at least) the first' three satellites cannot be eclipsed at the same time: for in the simultaneous eclipses of the second and third, the first will always be in conjunction with Jupiter, and vice versa.
Page 60 - ... of the planet. The surface of the ring is separated in the middle by a black concentric band, which divides it into two distinct rings. The edge of this ring, being very thin, sometimes disappears ; and, as this edge will present itself to the sun twice in each revolution of the planet, it is obvious that the disappearance of the ring will occur about once in 15 years ; but under circumstances oftentimes very different. The intersection of the ring and the ecliptic is in 5•...
Page 4 - This motion changes into epicycloids the ellipses of the planets and comets> which revolve round the sun. The sun appears to have a particular motion, which carries our system towards the constellation of Hercules. The apparent diameter of the sun, as seen from the earth, undergoes a periodical variation. It is greatest when the earth is in its perihelion ; at which time it is 32 35",6 : and it is least when the earth is in its aphelion ; at which time it is 31
Page 47 - The rotation of the moon on her axis it equal and uniform, and is performed in the same time as the tropical revolution in her orbit; whence she always presents nearly the same face to the earth. But as the motion of the moon in her orbit is periodically variable, we sometimes see more of her eastern edge, and sometimes more of her western edge ; which appearance is called the Iteration of the moon in longitude* The axis o( the moon is inclined to the plane of the ecliptic in an angle of 88° 29...
Page 31 - Her orbit is inclined to the plane of the ecliptic in an angle of 5° У ; but this inclination is variable. The greatest inequality, which sometimes extends to 8...
Page 48 - The cvection ; whose constant effect is to diminish the equation of the centre in the sjzigies, and to augment it in the quadratures. If this diminution and increase were always the same, the evection would depend only on the angular distance of the moon from the sun ; but its absolute value varies also with the distance of the moon from the perigee of its orbit. After a long series of observations, we are enabled to represent this inequality by sup.
Page 43 - Satellites. The number of satellites in our system, at present known, is eighteen = namely, the Moon which revolves round the earth ; four that belong to Jupiter, seven to Saturn, and six to Uranus. The moon is the only one visible to the naked eye. They all move round their primary planets, as their centre, by the same laws as those primary ones move round the sun : namely, I.